Bag closing and thread cutting device



March 26, 1963 E. H. SCHARMER, JR 3,082,718

BAG CLOSING AND THREAD CUTTING DEVICE Filed NOV. 28, 1960 4 Sheets-Sheet 1 INVENTOR. female I!- .Sumnnaz .Ze

March 26, 1963 E. H. SCHARMER, JR 3,082,713

BAG CLOSING AND THREAD CUTTING DEVICE Filed Nov. 28, 1960 4 Sheets-Sheet 2 FIE. E?

ENTOR. Eamon: b. Scmmuaeh BY J I F] @mmw drink/ray;

March 26, 1963 E. H. SCHARMER, JR 3,08

BAG CLOSING AND THREAD CUTTING DEVICE Filed NOV. 28, 1960 4 Sheets-Sheet 3 l6 v F1 ca. :5

EW" l L INVENTOR. Emmna Ii Sea/mum Ji Jinan!" United States Patent 3,082,718 BAG CLOING AND THREAD CUTTING DEVICE Edward H. Scharmer, Jr., Minneapolis, Minn., assignor to Minneapolis Sewing Machine, Inc., Minneapolis, Minn, a corporation of Minnesota Filed Nov. 28, 1960, Ser. No. 72,244 4 Claims. (Cl. 11211) The present invention relates to thread cutting devices for sewing machines and more particularly to an automatic device for cutting the chain stitch used to close bags so there is a predetermined amount of thread extending outwardly on both ends of the bag.

Present devices for automatically cutting the chainstitch formed when sewing a bag do not operate satis factorily and leave uneven or excessively long lengths of stitching on the bag ends. These uneven lengths present an untidy appearance and cause interference and damage when the bags are stored and handled. Most of the devices in use have no support for the stitched thread on the leading end of the bag and obtaining a predetermined length of lead stitch is extremely difficult.

The present invention discloses a device that uniformly severs the chain-type stitching on both the leading and the trailing edges of the bag responsive to the position of the leading and trailing edges of the bag with respect to the needle. A support for the chain-stitching is provided to insure a uniform length of stitching on the leading edge of the bag as the stitching will not be allowed to sag but will be supported and guided so the knife will leave a predetermined length of stitching every time it operates.

The cutting device consists of a solenoid that is operated by a microswitch that controls the flow of electricity to the solenoid. Said microswitch is in turn actuated by a cam that is rotated by a bag follower. The solenoid forces a knife against the thread to sever it at a prede' termined distance ahead of the bag as the bag moves into the sewing machine and also cuts the stitching an equal distance behind the bag after it has been sewn. The solenoid is energized an exact length of time to put the full force of the solenoid on the knife when it is cutting and to immediately release the knife and thereby insure satisfactory operation.

It is an object of the present invention to present a device severing the chain-stitching from a bag-closing machine a predetermined distance ahead of and behind the bag.

In the drawings,

FIG. 1 is a rear elevational view of a bag sewing machine with a bag in place for sewing;

FIG. 2 is a front elevational view of a bag sewing machine showing a device made according to the present invention installed thereon;

FIG. 3 is a sectional view taken as on line 3--3 in FIG. 2;

FIG. 4 is a sectional view taken as on line 4--4 in FIG. 2;

FIG. 5 is a partial top plan view of a thread cutting device made according to the present invention and showing a thread support shoe yieldably moving to allow a bag to pass underneath;

FIG. 6 is a partial top plan view of the device of FIG. 5 showing a bag that has been sewn and a thread support shoe in position to support the trailing chainstitching;

Patented Mar. 26, 1963 In the drawings and the numerals of reference thereon, a bag sewing machine 10 is driven by an electric motor 11 through a V belt 12 drivably mounted on a motor sheave 13 and a driven sheave 14. A control lever 15 is connected by a link 16 to a clutch assembly 17 that will engage or disengage the drive sheave to drive the sewing machine. The sewing machine 10 and attached motor 11 are suspended from a support member 18 with a cable 20 and a hook 21 that engages a bracket 19. The sewing machine is suspended at a convenient height so the top section 22 of a bag 23 that is being carried on a conveyor 24 will pass underneath a presser foot 25 of the sewing machine 10 and into the stitching needle 26 where it will be sewed closed with a chain-stitch. Two balls of thread 27, 27 that are utilized in the stitching are supported on a tray 30 connected to cable 20. A spring clip 31 serves to maintain tension on the thread.

A support shoe 32 is pivotally attached to a pair of rods 33, 33 that are slidably mounted in a support block 34 that in turn is mounted to sewing machine 10. Each I of rods 33, 33 has a collar 38 and a spring 35 mounted FIG. 7 is a top plan view of the device of FIG. 5 showthereon and positioned to resiliently urge the shoe 32 against a work plate 36 of the sewing machine. Shoe 32 is positioned ahead of the needle and presser foot and on a plane below the needle so any of the chainstitching, such as 28, formed by the sewing machine will be fed onto and supported by said shoe 32. Rods 33, 33 are positioned to allow a first portion of shoe 32 to remain in contact with work plate 36 when a second portion of shoe 32 moves to allow a bag to pass through, as best seen in FIG. 5. As the bag moves past the shoe 32 the shoe continues to follow under the stitching formed in the bag. A portion of the shoe 32 will move into contacting relationship with work plate 36 as soon as the bag moves clear of the presser foot 25, and thus will support the trailing chain-stitching before it sags or moves out of place.

A plunger 37 is slidably positioned in support block 34 and extends therethrough. A knife head 40 with a replaceable blade 41 is fixedly attached to plunger 37 and is situated at substantially right angles to the chain stitching and with the blade positioned substantially parallel to an anvil block 42 that is mounted on a plane parallel with work plate 36. Plunger 37 is positioned to slide in a direction substantially perpendicular to the direction of travel of the bag and chain-stitching. Knife blade 41 is positioned immediately adjacent shoe 32 on the end away from the presser foot so that when the knife is actuated to cut the chain-stitch an exact length of stitching will be left between the needle and the knife. Shoe 32 supports and guides the chain-stitching and the stitching will be properly positioned when the knife is actuated so an accurate cut will always be obtained.

A portion of plunger 37 extends beyond block 34 in a direction away from the knife blade and has a lug 43 attached thereto. A return spring 44 is slidably fitted over a guide rod 45 that is fastened to lug 43 and slidably fitted in block 34. Spring 44 resiliently urges the knife and plunger away from the cutting block 42 and the chain-stitching. A solenoid 46 is mounted on sewing machine 10 and has a tang 47 that is positioned to engage lug 43 and force knife blade 41 against anvil block 42 when the solenoid is energized.

A microswitch 50 is actuated by a cam wheel 51 with a lobe 57 acting on a roller 52 that is rotatably attached to the microswitch actuator lever 53. Cam 51 is fixedly attached to a shaft 54 that is rotatably mounted in support block 34 on an axis substantially parallel to the upright side of a bag that is being sewed. A cam actuator rod 55 is fixedly attached to shaft 54 adjacent an opposite side of support block 34 and extends to engage a bag that is moving through the sewing machine. A spring 48 resiliently urges rod 55 in direction to rotate clockwise as seen in FIGS. 5, 6 and 7. A stop 56 extends to engage a portion of block 34 and prevent the actuator rod from moving too far in clockwise direction.

A time controlled circuit illustrated in FIG. 8 is used to energize the solenoid 46 for a predetermined time regardless of the time it takes the lobe 57 to pass by the roller 53. The circuit receives power from a 110 volt, 60 cycle source and includes a relay 60, a condenser 61, a resistor 62 and a rectifier 63. The rectifier 63 is normally connected across the condenser 61 to keep it charged. When the microswitch is operated by lobe 57 of cam 51, the rectifier 63 is disconnected and the relay 60 is activated. This cuts out the microswitch completely, connects the solenoid 46 across the line, and connects the condenser 61 across the relay coil to hold this relay in until and as the condenser discharges. The rate of discharge is determined by the characteristics of the relay coil, condenser and of resistor 62; and will be of value to hold the relay closed until the solenoid has had opportunity to force the knife blade down onto the stitching with full force.

The relay 60 cannot operate again until the condenser 61 is recharged. As long as the cam lobe 57 engages the wheel 53, the rectifier 63 is out of the circuit so that this cannot happen. Consequently, regardless of the time interval during which the microswitch is activated, the time which the solenoid is energized is constant. Energizing the solenoid 46 for 0.012 second has been found to be most satisfactory.

Operation Assuming the sewing machine is constantly running, a bag 23 to be closed is moved toward the sewing machine by conveyor 24, engages actuator rod 55, is guided 'under presser foot 25 and the top of the 'bag is sewed. When the bag is advanced to a position as shown in FIG. 4, lobe 57 on cam 51 actuates microswitch 50 and the solenoid 46 is energized for a predetermined length of time that is controlled by the time controlled circuit. When the solenoid is energized, the tang 47 imparts an impulse of force to the lug 43 and the knife blade is forced down against the anvil with the full force of the solenoid and severs the leading stitching to a predetermined length. Ideally the force from the solenoid will be applied until the stitch is cut. As the plunger and the tang of the solenoid are not joined, the plunger will override the tang and complete the cutting stroke even if the solenoid is not energized for the full stroke length. This insures complete cutting of the stitching after the parts have been used and worn.

As the solenoid is no longer energized after the stitching is severed, spring 44 is free to return knife blade 41 to position away from the bag and stitching.

The work plate 36 and the upright wall of shoe 32 form a guide for the leading stitching so it may be pushed ahead of the bag without bending or moving out of line with the knife. Without this type of support for the leading stitching it is difficult to get a uniform length of lead thread. The shoe keeps the thread from sagging and guides it to an exact position for cutting by the knife.

The bag 23 moves through the machine to a position as shown in FIG. 5. The leading edge of the bag top section 22 slides under the rear end portion of shoe 32 against the action of springs 35 and the front end of shoe 32 continues to support the leading chain stitch. The shoe 32 moves to position as shown in FIG. 3 as the bag advances. At all times the shoe 32 is below the chain-type stitching.

When the bag has been completely closed and moves out of the machine, the rear end of the shoe 32 moves under the urging of springs 35 against wall 36 and thereby supports the trailing chain stitch before the stitching can sag. This position is best seen in FIG. 6. When the bag moves further, the shoe 32 again seats entirely on wall 36 and supports the chain stitching as before.

As the bag advances after the initial severing of the chain stitching, the actuator rod 55 moves with the leading edge of the bag and rotates the cam 51 to position where the microswitch 50 is in its normal position and the solenoid 46 is not energized. The cam remains in this position as the bag slides past the rod 55 during the sewing operation. After the bag has been sewn it moves clear of the rod and the actuator rod moves under the action of spring 48 until lobe 57 of the cam again moves the microswitch 50 to energize the solenoid and thereby sever the trailing chain stitching as shown in FIG. 7. The rod 55 is thereby automatically positioned to contact the next bag that is to be sewed shut and the process will repeat. The shoe 32 also holds the trailing chain stitching in position so predetermined length of stitching remains on the bag. The length of the chain stitching on the bag may be controlled by regulating the length and position of actuator rod 55 and the shape and position of cam 51.

The cutting device presented insures even lengths of leading and trailing stitching on all bags that are sewn without any attention from an operator. The thread support shoe prevents the occurrence of inaccurate lengths or misses from thread sag.

What is claimed is:

l. The combination with a bag sewing machine having a substantially horizontally reciprocating needle moving in relation to a substantially vertical work plate to form chain-type stitching used for sewing a bag, passing between the needle and work plate, closed, of: a cutting device including a support shoe positioned with respect to said needle on a plane below said needle and adjacent said needle in the direction of travel of a bag that is being sewed, a first rod pivotally attached adjacent an end thereof to said shoe adjacent a first end of said shoe, a second rod pivotally attached adjacent an end thereof to said shoe adjacent a second end of said shoe, a support block fixedly mounted with respect to said sewing machine, both of said rods being slidably mounted on their respective longitudinal axes in said support block and positioned to allow said shoe to move transversely to the direction of travel of said bag, resilient means urging said shoe toward said work plate, a plunger with attached knife blade slidably mounted with respect to said support block and movable to position to cut said stitching, a solenoid operably associated with said plunger, resilient means urging said knife away from said cutting position, and means responsive to the movement of said bag for energizing said solenoid.

2. The combination as specified in claim 1 wherein said means for energizing said solenoid includes an electric switch in a solenoid energizing circuit, cam means operably associated with said switch, actuator means operably associated with said cam means to move said cam means to position to actuate said switch responsive to the movement of a leading edge of said bag toward said needle and to actuate said switch responsive to the movement of a trailing edge of said bag away from said needle.

3. The combination as specified in claim 2 wherein said solenoid is energized for a predetermined length of time independent of the length of time that said electric switch is actuated.

4. The combination with a bag sewing machine having a substantially horizontally reciprocating needle moving in relation to a substantially vertical work plate to form chain-type stitching used for sewing a bag, passing between the needle and work plate, closed, of: a cutting device including a support block fixedly attached to said machine, a first rod slidably mounted in said support block, a second rod slidably mounted in said support block and movable substantially parallel to said first rod, a stitch support shoe pivotally attached adjacent a first end thereof to said first rod and pivotally attached adjacent a second end thereof to said second rod, said shoe being positioned below said needle and adjacent said needle in the direction of travel of a bag that is being sewed, resilient means urging said shoe into contacting relationship with said work plate, said shoe being of configuration to yieldably move to allow each of Said end portions of said shoe to move to allow a bag to pass between said end portion and said work plate with the opposite end portion of said shoe in position against said work plate, an anvil attached to said machine and substantially aligned wit said work plate, a plunger with attached knife slidably mounted with respect to said support block and movable to position to cooperate with said anvil to cut said chain stitching, resilient means for urging said plunger in direction away from said anvil, a solenoid mounted with respect to said sewing machine and having a tang positioned to contact said plunger to force said attached knife to cut said stitching when said solenoid is energized, an electric switch movable to a first position for activating an electric circuit for energizing said solenoid, said circuit including means to control the length of time the solenoid is energized regardless of the length of time said switch is in said first position, a cam mounted with respect to said switch, a bag contacting member operably associated with said cam to move said cam to position to move said switch to said first position responsive to movement of a leading edge of said bag toward said needle and responsive to movement of a trailing edge of said bag away from said needle.

References Cited in the file of this patent UNITED STATES PATENTS 1,738,186 Krasa Dec. 3, 1929 2,151,438 Pierce Mar. 21, 1939 2,569,396 Bates Sept. 25, 1951 

1. THE COMBINATION WITH A BAG SEWING MACHINE HAVING A SUBSTANTIALLY HORIZONTALLY RECIPROCATING NEEDLE MOVING IN RELATION TO A SUBSTANTIALLY VERTICAL WORK PLATE TO FORM CHAIN-TYPE STITCHING USED FOR SEWING A BAG, PASSING BETWEEN THE NEEDLE AND WORK PLATE, CLOSED, OF: A CUTTING DEVICE INCLUDING A SUPPORT SHOE POSITIONED WITH RESPECT TO SAID NEEDLE ON A PLANE BELOW SAID NEEDLE AND ADJACENT SAID NEEDLE IN THE DIRECTION OF TRAVEL OF A BAG THAT IS BEING SEWED, A FIRST ROD PIVOTALLY ATTACHED ADJACENT AN END THEREOF TO SAID SHOE ADJACENT A FIRST END OF SAID SHOE, A SECOND ROD PIVOTALLY ATTACHED ADJACENT AN END THEREOF TO SAID SHOE ADJACENT A SECOND END OF SAID SHOE, A SUPPORT BLOCK FIXEDLY MOUNTED WITH RESPECT TO SAID SEWING MACHINE, BOTH OF SAID RODS BEING SLIDABLY MOUNTED ON THEIR RESPECTIVE LONGITUDINAL AXES IN SAID SUPPORT BLOCK AND POSITIONED TO ALLOW SAID SHOE TO MOVE TRANSVERSELY TO THE DIRECTION OF TRAVEL OF SAID BAG, RESILIENT MEANS URGING SAID SHOE TOWARD SAID WORK PLATE, A PLUNGER WITH ATTACHED KNIFE BLADE SLIDABLY MOUNTED WITH RESPECT TO SAID SUPPORT BLOCK AND MOVABLE TO POSITION TO CUT SAID STITCHING, A SOLENOID OPERABLY ASSOCIATED WITH SAID PLUNGER, RESILIENT MEANS URGING SAID KNIFE AWAY FROM SAID CUTTING POSITION, AND MEANS RESPONSIVE TO THE MOVEMENT OF SAID BAG FOR ENERGIZING SAID SOLENOID. 